The invention relates to vehicle safety systems including warning means which provide safety information for example to drivers of following vehicles.
A known warning means comprising a vehicle display system is described in WO93/15931 which provides a display system which indicates discrete ranges of deceleration of a vehicle and which can also provide a display to indicate that the vehicle is stationary. All the features of that display system are incorporated in this specification especially when referring to a progressive brake warning (PBW) or vehicle stationary indicator (VSI) display. A known ground speed measuring device is disclosed in WO92/01951 which uses a double horned radar device, again the teachings of that specification are incorporated herein.
The invention seeks, inter alia, to improve known vehicle display systems and ground speed measuring systems.
According to one aspect of the invention there is provided a safety system for vehicles comprising a controller fitted in use to a subject vehicle, sensor means fitted to the subject vehicle in use and operable to sense a distance of separation and/or a relative velocity of a trailing vehicle and operable to input data signals representative thereof to the controller, velocity sensing means operable to sense the velocity of the subject vehicle relative to the ground and to input to the controller a velocity signal representative thereof, wherein the controller is operable to processes the received velocity signal and data signals to determine the existence of an unsafe condition, and the safety system further comprising warning means controlled by the controller and operable to warn a driver of the trailing vehicle of the existence of the unsafe condition.
Preferably the controller is operable to determine the existence of the unsafe condition by determining a safe distance corresponding to a safety envelope to the rear of the subject vehicle within which any incursion by the trailing vehicle constitutes the existence of an unsafe condition.
This provides the advantage of assisting the driver of the trailing vehicle to more accurately determine the safe distance, drivers typically tending to underestimate the safe distance in the absence of any such warning system.
The safe distance may be determined to be substantially the safe stopping distance of a vehicle travelling at the velocity of the trailing vehicle.
The safe stopping distance may be determined to be proportional to the velocity of the subject vehicle.
Preferably the warning is terminated after the measured value reaches a safe value. The warning can be provided by a display operably carried by the subject vehicle and positioned for viewing by the driver of the trailing vehicle, and the display can comprise a row of lights.
The system may comprise means for warning that the subject vehicle is stationary. The system can further comprise means for providing warning of different levels of deceleration of the subject vehicle. The warning means can comprise an orange light display for the relative speed and/or relative separation conditions and a red light display for the vehicle stationary and/or levels of deceleration conditions. The relative separation and/or relative speed warning may be overridden by the level of deceleration warning.
The system in a preferred embodiment has a radar device having two receiver antenna which device operably communicates with a controller which is able thereby to determine the direction of motion of the vehicle, and warning means which is automatically actuated by the controller to provide a warning when the vehicle moves.
A further warning means can be automatically activated when the vehicle reverses and may comprise an array of lights and/or means for generating sound.
The controller may be operable to determine an enhanced safe distance corresponding to an enlarged safety envelope and the warning means may be further operable to indicate a first level of warning corresponding to incursion by the trailing vehicle into the enlarged safety envelope and a second level of warning which is more prominently presented to the driver than the first level of warning and corresponds to any incursion into the safety envelope.
The size of the enhanced safe distance and enlarged safety envelope will generally be predetermined so as to correspond to typical parameters appropriate for driving under adverse road conditions. These parameters may for example be stored in a look up table allowing the parameters to be determined from the signals received by the controller together with the parameters defining the normal safety envelope.
The safety system may comprise ground condition communication means operable to input to the controller a signal representative of the condition of the ground and or other driving conditions and wherein the controller is operable to determine the enhanced safe distance corresponding to the enlarged safety envelope according to the extent to which the ground condition communication means indicates adverse ground conditions likely to affect traction between the subject vehicle and the ground.
The enhanced safety distance and enlarged safety envelope may thereby be made adaptable to the prevailing driving conditions and the ground condition communication means would preferably function automatically to input data such as whether rain, ice or snow was presenting a driving hazard, the source of the data being either on board sensors or telemetric links to an external system providing relevant data.
Preferably the sensor means is operable to sense both the distance of separation and the relative velocity of the trailing vehicle and the controller is operable to determine whether the relative velocity of the trailing vehicle relative to the subject vehicle when entering the enlarged safety envelope is greater than a threshold value of relative velocity and, if so, is operable to actuate the warning means to indicate the second level of warning.
This has the advantage of delivering a warning with full prominence to the driver of the trailing vehicle before the trailing vehicle has reached the main safety envelope in order to give the maximum available warning to the driver that his closing speed to the subject vehicle is excessive.
In a preferred embodiment the ground condition communication means comprises means fitted to the subject. vehicle for sensing at least one of rain, snow and ice and communicating a signal representative thereof to the controller.
The sensor means for sensing the distance and velocity of the trailing vehicle may comprise a radar system transmitting and receiving radar pulses, from which received pulses information is derived sufficient to determine both the proximity and relative speed of the trailing vehicle.
The safety system may comprise communication means operable between the controller of the subject vehicle and a warning device fitted in use to the trailing vehicle, whereby the warning means is operable to indicate a warning to the driver of the trailing vehicle via the warning device.
The velocity sensing means may comprise a conventional speed sensing device fitted to the vehicle""s transmission train and may for example include a hall effect sensor.
The velocity sensing means may alternatively comprise a sensor mounted on the subject vehicle and responsive independently of elements of the subject vehicle""s transmission train to movement of the ground relative to the subject vehicle.
In a preferred embodiment the velocity sensing means comprises a sensor constituted by a doppler shift radar device.
An advantage of such sensing means is that it is free from the errors inherent in determining velocity via the transmission train which arise from variation in tyre diameter due to varying inflation pressure, tire wear or other factors.
The controller may also be operable to actuate an impact absorbing device deployed internally or externally of the subject vehicle.
The impact absorbing device may comprise an air bag inflatable so as to be deployed externally of the subject vehicle and/or bumpers extensible by means of hydraulic rams operable to absorb energy upon impact.
The effects of impact may thereby be attenuated prior to the point of collision between the subject vehicle and an object which may be a trailing vehicle for example.
Another aspect of the invention provides a system for vehicles having means for determining the magnitude of acceleration and deceleration of the vehicle and output means enabling the magnitude of acceleration and deceleration to be interpreted by a third party remote from the vehicle. The output means can comprise a visible display having a first form of representation for acceleration and a second form of representation for deceleration. The display can comprise an array of lights mountable on the side of a vehicle. A first coloured array can represent acceleration and a second coloured array can represent deceleration and preferably the number and/or intensity of actuated lights of a given colour represents the magnitude of the acceleration or deceleration.
This aspect of the invention has application for example to racing cars and motorcycles where a visible display mounted on either or both sides of the vehicles enable spectators and cameras to perceive the rate of acceleration or deceleration of the vehicle thereby adding interest and enjoyment. Such displays would not be visible necessarily to the leading or trailing drivers so as to cause minimal interference with the conduct of racing.
Also disclosed herein is a management system for a vehicle comprising a ground speed sensor having means for determining the true speed and direction of travel of the vehicle and means for communicating the speed and direction of travel of the vehicle to a controller which operably controls a second vehicle device in response to the speed or direction information.
Preferably the system is adapted to perform any one, or any combination of the following functions: active sensing for cruise control, or comparison with actual wheel speeds for anti-lock braking systems and/or active traction control, provision of any one of the following: driving speed over ground display, distance covered, fuel economy measurement, elapsed journey time and estimating time of arrival at destination, average fuel economy over journey; automatic triggering of airbags; change gear in electronic automatic transmission vehicles.
Such a system can also include the features of all the other aspects of the invention.
According to a further aspect of the invention there is disclosed a safety system for vehicles comprising an antilock braking system fitted to a subject vehicle and operable to regulate operation of the subject vehicle""s brakes in response to a signal generated by a speed sensor and representative of the speed of the subject vehicle relative to the ground, characterised in that the speed sensor is a radar system operable to direct radiation towards the ground and to determine the speed by receiving and analysing radiation reflected from the ground.
The radar system may be operable to determine speed by measurement of a doppler shift in the frequency of the reflected radiation.
According to a further aspect of the invention, there is disclosed a safety system for vehicles comprising at least one impact energy absorbing device fitted to a subject vehicle, sensor means fitted to the subject vehicle and operable to detect the proximity and closing speed of an object external to the subject vehicle, determining means responsive to output signals of the sensor means for determining whether the object is about to impact with the subject vehicle and actuating means responsive to the determining means to actuate the at least one impact energy absorbing device so as to be deployed at a position externally of the subject vehicle so as to be between the object and the subject vehicle.
The impact energy absorbing device may be an inflatable bag device comprising two or more inflatable bags deployed when inflated so as to constitute successive layers including an inner bag proximate the subject vehicle and an outer bag distal to the subject vehicle.
The safety system preferably comprises deflation means operable to deflate one or more of the bags in response to pressure within the respective bag exceeding a predetermined pressure level.
The deflation means may be operable to deflate bags in successive layers at pressure levels which decrease progressively from the inner bag to the outer bag whereby in use the outer bag is deflated prior to deflation of the inner bag in response to impact between the object and the subject vehicle.
The deflation means may comprise rupturable membranes forming parts of side walls of respective bags and arranged to rupture at respective predetermined pressure levels.
In a preferred embodiment the air bag device comprises three inflatable bags.
The preferred comprising a plurality of air bag devices located so as to be deployed at the front, rear, left side and right side respectively of the subject vehicle.
Alternatively the impact energy absorbing device comprises at least one bumper extensible by means of hydraulic ram means capable of absorbing energy when the bumper receives an impact.
A yet further aspect of the invention provides a safety system for vehicles comprising a ground speed measuring device and/or input detection means and a controller operable to activate a spraying device to release safety chemicals such as foams when an accident is likely.
Another aspect provides an antenna for a radar system comprising means for coupling the antenna to a radar system to enable electromagnetic radiation from the radar to be transmitted through the antenna and for reflected radiation to be passed back to the radar-through the antenna, said antenna further comprising a body portion which is wedge-shaped. The wedge can taper to a tip of less than 1 mm thickness. Preferably the antenna is made at least partially of PTFE.
Yet another aspect of the invention provides a housing for a radar system having means for communicating electromagnetic radiation into a waveguide which directs the radiation along two paths in two separate directions each leading to an output, the housing being adapted to accommodate receiving antennas in each of the radiation paths, the housing further comprising wedge-shaped antenna at the outputs for transmitting and collecting reflected radiation. The receiving antenna accommodation can be separated by half a wavelength of the radiation.
Another aspect of the invention provides a housing for a radar system having an inlet for electromagnetic radiation which leads to a waveguide which directs the radiation along two paths to two separate outlet/inlet horns wherein the horns taper along their length in one transverse dimension relative to their longitudinal axis.
The horns can taper outwardly. The horns can be turned inwardly such that radiation emitted from one horn is directed to intersect with the radiation from the other. Preferably the housing is adapted to accommodate two receiving dipoles equidistantly spaced from a point where the two paths meet.